It is enough to take courses in Icelandic, you do not have to take examinations as well. You will need to attend a 150 lessons in Icelandic  held by an acknowledged party.

You can also submit a confirmation from the University of Iceland or Icelandic secondary school.

If you have already studied Icelandic , you can take an Icelandic language assessment test held by an educational institution acknowledged by the Directorate of Education. If you pass that examination, you do not have to take a course in Icelandic.